


Wait ... What?

by LazySintastic13 (EmeraldWriter)



Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell, Breastfeeding, Fellcest - Freeform, Lactation Kink, M/M, Multi, Spicycinaroll - Freeform, Underfell Papyrus, Underfell Sans, kustard - Freeform
Language: English
Status: Completed
Published: 2017-03-26
Updated: 2017-03-26
Packaged: 2018-10-10 20:16:29
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 2,707
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/10446516
Author URL: https://archiveofourown.org/users/EmeraldWriter/pseuds/LazySintastic13
Summary: Sans wondered how Red managed to raise Fell.So he had to ask.





	1. Chapter 1

**Author's Note:**

  * For [Prazeodymium](https://archiveofourown.org/users/Prazeodymium/gifts), [amynastre](https://archiveofourown.org/gifts?recipient=amynastre).



Both Red and Sans were lazing on the couch as they watched a show without much of an interest but to waste time; their condiments at hand. Their brothers won’t be back until later and it wasn’t as if they were going to do the chores assigned to them. Too much effort.

Then, a thought hit Sans suddenly, and he was curious so he had to ask. “Hey, Red?” He continued when he heard a grunt in reply. “You told me that it was hard to find resources back in your world right?”

Red quirked a brow ridge. “… Yeah?”

“Oh but, if it’s an uncomfortable topic then—”

“Just ask the damn question already.”

“Well, if you insist.” Red rolled his eye lights. “When your brother was baby bones, how did you acquire milk on a daily basis to feed him? I mean, in my case, I’d just buy it at the market, but maybe it’s the same for you? Or not?”

“Oh, that? I breastfed him.”

Sans spat out his ketchup as he coughed. His cheekbones tinted blue. “W-What?”

Red looked at Sans in confusion. “I said I breastfed him.”

“Y-Yeah. I heard.” Sans felt his face heat up and he swore that he was starting to sweat.

“You okay?”

‘Why is he so casual about it?!’ “H-Huh? Yeah. I-I’m good.”

“Your face is blue.”

“Right.”

Red snorted. “You want to see my tits or something?”

“What?! How did you get to that?!”

“What? Am I wrong that you’re _not_ curious?”

Sans fidgeted in his seat. “Maybe … A little.”

Red rolled his eye lights again. ‘What a baby bones.’ With his magic, his thoracic cavity expanded beneath his shirt. He was well-endowed but fit his small physique nevertheless. “So I basically just transform what I eat to milk and fed my bro that way until he was old enough to eat more chewable foods.” Red explained the method as he casually lifted shirt off to show Sans his chest.

The latter jumped in his spot, inwardly screaming at the situation he got himself in.

Red wanted to laugh, but managed to hold it in. It was rare to rile the other, so he was going to continue _milking_ as much reaction as he could. It was so fun to tease. “You wanna cop a feel? Here.” He took Sans’ hand before the skeleton could comprehend what was happening and placed it on a boob.

Sans was really sweating now, and no doubt his face was a darker blue. The soft and smooth texture under his metacarpals were giving him the urge to squeeze just to see how soft it was. But he was going to refrain or so help him star—

“Why don’t you give it a squeeze?” Red pressed Sans’ hand harder, and Sans was definitely sure that he combusted.

“Actually, since you’re curious, do want to have a taste of _my milk_?”

Sans eye lights disappeared and Red stared at him with a smirk. The silence hung over them for moments on end.

That is …

Until Sans ported out.

Seeing the latter pop out of sight, Red laughed to his heart’s content. He undid his magic as he put his shirt back down and his chuckles slowly dyed out to having a satisfied smile adorning his features.

That was certainly one way to get rid of boredom.


	2. Continuation

**Summary for the Chapter:**

> The Papyruses gets curious as Sans ignores Red for some strange reason.

**Notes for the Chapter:**

> Poly here.

Days have passed and it was easy to see that Sans was avoiding Red at all costs. Couldn’t even stay in the same room as him. Which got their siblings worried; especially Papyrus.

Wanting to get to the bottom of it, he asked Red when Sans had ported out, most likely to his room after dinner. “Are you and my brother fighting?”

“Fighting? Nah.” He smirked. “He’s just probably not over how I raised my brother.”

“Raised me?” Fell came to them shortly after he finished doing the dishes; he was drying his hands with a small towel.

“He was curious as to how I got you milk when you were baby bones when our world is shit.”

“Language!” Papyrus said, but now he was curious as well. “And it shocked my brother that much? Did you not buy it from a market? That’s what Sans told me where he gets them from.”

And when Fell thought about it, he also didn’t know how his brother did it. He was just baby bones, and even after that, he never wondered until today. He waited quietly for the small skeleton to answer, now he needed to know since it surprised the counterpart so much that he was avoiding Red.

Red scratched the back of his neck, unsure if he was okay to relay the information to them. It was fine with Sans … he guessed that maybe it’d be fine with their brothers too. He’ll get a kick out of their, he expect, disgusted reaction—especially his brother. “Are you sure you want to know? I don’t mind, but there’s no turning back.” He grinned widely after a bit of snickering.

Papyrus and Fell didn’t quite know if they should hear about it with how ominous Red was making it. But the two were simply too curious to let it go. They looked at each other, relaying a secret message that Red will never know simply by eye contact, before nodding to him. Nothing as great as them couldn’t handle.

 _Well, all right then_. “I told Sans that I breastfed my little bro. That’s how I got milk daily.”

Moments passed and no one uttered a sound. Red waited for the reactions, only to be disappointed.

“What’s that?”

Red wanted to face palm. He could understand Papyrus, but even his own brother? He’s a failure as the older one.

“Err.“  _Do I even want to explain?_  "I’m sure you could find out about it in the librarby.”

“Just tell us!” Fell crossed his arms impatiently.

“Nah. I’m going to have to pass. Good night.”

“Wai—” but Red ported out before Papyrus could stop him.

The two skeletons stood there before turning to look at each other. “So …”

“Of course.”

Papyrus nodded. “We’ll go to the librarby tomorrow morning then.”

* * *

 

**(NSFW-ish version…..)**

Continuing from here:

“Just tell us!” Fell crossed his arms impatiently. 

Red raised both hands in surrender. “All right, all right. Basically, I use my magic to grow a pair of tits and milk will come out once I transform the magic I ate into milk.”

Papyrus eye sockets widened. “You can do that?”

Red shrugged. “Not a big deal.”

“Can you do it now? Can we see?”

Red raised a brow ridge to which he looked at his brother and saw the curiosity practically oozing from him as well. Well, if it’s to educate them. He supposed he could do it. What’s the harm?

“Sure, why not. I just ate too so I should be able to do it.” He headed over to the couch, the two following after him. The small skeleton seated himself, his back rested on the cushion before summoning his breasts.

He could see them look at him in awe, and it gave him a rather strange feeling. But he continued on in a professional manner. Education purposes, he reminded himself—all for educational purposes.

He lifted his shirt up, and the tall skeletons sat on each side of him, staring at the conjured magic.

“So how do you get the milk?”

Red pointed at his pert nubs. “You would suck on these and milk will come out.”

“Oh! May I have a taste?”

Red was getting that weird feeling again, and he didn’t know if he should let him or not. But he reminded himself that it was for educational purposes so he gestured for the latter to go ahead.

Papyrus went to the floor to be at level of Red’s chest, his elbows supported on the seat cushions. He leaned forward, unconsciously summoning his tongue for a lick before he closed his mouth on it and sucked.

Red almost jumped. It has been so long since he’d done it so the sensation was new and yet familiar. He looked to his brother who watched Papyrus with rapture before turning his attention to him. “Go ahead.”

Fell followed Papyrus’ lead and began sucking on the other one.

Red could feel the milk flowing out of him and he took a deep breath.

“Wowie! Your milk is delicious, Red! I’ve never had anything like it before.”

Red snorted. He supposed he could take the compliment. “Thanks, Paps.”

“It certainly is better than the market milk.” Fell added, to which Red flicked his forehead.

“Of course it’s better. Mine is organic, you brat.”

“Nyehehe, may I have some more?”

Red shrugged. “Sure.”

And the two skeletons dug back in their task.

It was calming. Red placed his hands on the back of their heads; not really to apply any pressure. It’s just there. And he almost found himself humming before realizing that it may a bit embarrassing on his part so he refrained from doing so.

But then, something strange was happening as moments went on. His nipples were becoming sensitive from the constant caresses of their tongues and he groaned when nibbling came into play. “H-Hey. Stop that.”

Red whimpered when his breasts were being massaged and they sucked harder on his tits. More and more milk poured out and he could hear the gulps being taken.

“So tasty.” Fell pinched at the nub, causing Red to squeal as bits of milk squirted out.

 _Shit. It’s getting out of hand. I need to stop—_ Red keened when Papyrus bit his nipple; the milk squirting into the other’s mouth with some dripping down his jaw that he promptly got with his tongue.

“You’re like a fountain, Red. It just keeps coming.”

The small skeleton panted, looking at them with half lidded eyes. “Y-you’ve had your fill, right? Let’s stop.”

“But you haven’t.” Fell looked at the dimmed red glow in his shorts.

Red’s face flushed and the predatory looks he was receiving was increasing the glow. The small skeleton inwardly cursed his arousal.

“Don’t worry. We’ll help take care of it.”

Though before Papyrus or Fell could start, Sans appeared behind the couch, looking at them with an annoyed expression.

He didn’t bother to say a word before putting his hand on Red and porting them out.

Fell clicked his tongue and Papyrus simply frowned.

“Your brother can be so annoying.”

“That may be true, but at least the plan worked!”

“Indeed.”

“Your brother makes really delicious milk.”

“The best.”

“Do you think he would be willing to produce them into bottles?”

“I highly doubt it. I don’t think your brother will share once he gets a taste of it.”

“That’s true.” Then Papyrus beamed. “At least we can always ask Red when he’s willing to give some for us. I’d hate to never taste it again.”

“That’s a given.”

“Nyehehee!”

**Notes for the Chapter:**

> Kustard goodness in the next.


	3. Bone-us Content

**Summary for the Chapter:**

> Sans wants a taste for himself.

Red trembled at his spot on the bed as he met Sans’ glare, the skeleton hovering over him—making him feel cornered.

“I c-can explain.”

Sans growled. “Can you?

Red’s face flushed, his eye lights looking back and forth from Sans to elsewhere constantly. "I was d-doing it for educational p-purposes.”

“ _Right_.”

Hearing the clipped tone, Red knew that he was in deep shit.

“So why the hell are you turned on, huh?” The skeleton sat upright to stare down at reddened area of the other’s shorts.

“It-It’s not like I meant to! They were pulling too hard and—” Sans pulled at the waist band with both hands and removed the clothing to throw it away. “Hey!”

“You’re already  _drenched_.”

Red sputtered, turning redder. “L-Like I said, they— _Nngghhh!_ Oh fuck! Aaaaahh!”

Three fingers made loud squelching noises that were unavoidable to not acknowledge.

“Do you hear it? You’re such a slut. I can already fit three in.”

“I-I—” Red threw his head back as hands clenched the covers of the bed. He screamed when Sans leaned forward and sucked on his clit. Tears pricked at the corners of his eye sockets, panting heavily whilst his legs trembled at the assault. “Come. _Coming!_ ”

The skeleton whimpered as he climaxed and Sans pulled back to watch the mess. Licking his mouth, he pushed down his shorts to free his already hardened cock, leaking with precum, just waiting to be surrounded by that warm and tight heat.

Sans lined himself up against Red’s entrance and slowly pushed inside. Both groaned at the feeling and Sans bent forward to kiss Red. Tongues meshed together in a feverish dance and moans were swallowed when Sans began canting his hips.

Red pulled away, a string of saliva breaking connection and trailed down his jaw. “S-Stop moving. Sensitive.”

Sans grinned. “Yeah, you are. And I love it.” His eyes trailed to pert nipples that milk began spilling out from. “But you’re right. There are more important things to attend to.” He cupped the other’s breasts, moving to the hardened nubs to rub and squeeze at them; the milk poured out in thin trickles.

“F-Fuck.”

Sans laughed breathlessly. “Yeah. Thanks for the meal.” He leaned down to lick and suck on a tit, drinking down the tasty milk.

Red tried to smile, coming to be crooked as he wrapped his arms around Sans. “Sheesh. J-Jealous much?”

Sans glared, and slammed his cock into Red. The latter gasped, but let out a choked laugh still.

“Y-You’re such a baby b-bones.” For his cockiness, Sans bit particularly hard that it made him scream. “Sorry! I’m sorry!”

Sans let go, licking around the bite mark to ease the pain. He looked to Red, who met his gaze with half-lidded and teary eyes, his silent question answered with a nod and a grunt.

The skeleton began to move, starting out slow, not wanting to hurt his partner despite supposedly punishing him. His pace increased gradually until he was slamming hard and deep inside the pulsing and tightening heat.

Red was beyond caring if he could be heard outside their thin walls as he moaned and screamed with abandon. “Fuck yes! _Sans!_ Harder! _Aaah!_ _Yes!_ ”

Sans paused to press both of Red’s nipples together and put them in his mouth to drink more of the milk.

“Sa— _aaaah!_ ”

Sans resumed fucking Red as he sucked on his tits. Some of the milk spilling from his mouth, trailing down the sides of the breasts.

“Shit,  _Sans!_ ” Red could feel the building coming close, stronger than before.

Sans let go to replaced it with his hands on the abused magic flesh instead. Panting just as hard as Red, he was close as well. “Then cum, Red. Fucking c _um on my cock_." And Sans squeezed at Red’s breasts, spraying thinned out milk all over, making both skeletons wet and the bed damp.

Red saw white as his essence gushed hard, and just as he came, he felt himself being filled to the brim in return. He clutched onto the sheets, tears falling to the sides of his face as he breathed deeply to rest from his high. He groaned when he felt some of San’s spunk spill out, there was so much inside of him.

"G-Geez. Talk about p-pent up. Heh. Were you saving  _your_  milk f-for me?” The skeleton grinned at Sans who rolled his eyes and proceeded to embrace Red, still inside of his partner. “H-Hey, get out.”

“Nah. Tired. Comfy.” Sans rested his head on the other’s chest, using them as his boobs as pillows.

“We are not sleeping like thi—Hey!”

“G’night.”

Red sighed in defeat when he could hear the faint snore from his partner. The latter falling asleep easily much to his dismay. “… You’re such an ass.”

Well, if Sans wasn’t about to move, and considering how exhausted he was, he supposed he could fall asleep as they were.

So Red closed his eyes and allowed sleep to take him away.

When he gets his energy back; however, he was going to do his damnest to avoid their brothers. There was no way he could look at them in the face when they were sure to have heard the embarrassing noises he made. 

It was clear that Sans was dead to him.

**Notes for the Chapter:**

> The smut was meh. Sorry.

**Author's Note:**

> The thought just came to. Lol.


End file.
